Geert reported issues regarding checksum complete and UDP.
The logic introduced in commit 7e3cead517
("net: Save software checksum complete") is not correct.
This patch:
1) Restores code in __skb_checksum_complete_header except for setting
CHECKSUM_UNNECESSARY. This function may be calculating checksum on
something less than skb->len.
2) Adds saving checksum to __skb_checksum_complete. The full packet
checksum 0..skb->len is calculated without adding in pseudo header.
This value is saved in skb->csum and then the pseudo header is added
to that to derive the checksum for validation.
3) In both __skb_checksum_complete_header and __skb_checksum_complete,
set skb->csum_valid to whether checksum of zero was computed. This
allows skb_csum_unnecessary to return true without changing to
CHECKSUM_UNNECESSARY which was done previously.
4) Copy new csum related bits in __copy_skb_header.
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
46fb51eb96